1. Field of the Invention
The present invention relates to a method for treating waste waters containing a surface active agent comprising a condensate, with formaldehyde, of a sulfonated organic compound such as an aromatic compound, a fused benzene ring compound or a hetero compound. It is a primary object of the present invention to provide a method according to which a surface active agent such as those mentioned above can be effectively removed from waste waters.
2. Description of the Prior Art
Surface active agents comprising a condensate obtained by condensing with formaldehyde a sulfonated organic compound such as an aromatic compound, a fused benzene ring compound or a hetero compound, are widely used in various fields as dispersing agents. The treatment of waste waters containing these surface active agents involves various problems. Since these compounds have a high molecular weight, they are not readily subject to biodegradation. Accordingly, although they are employed in various processes in such a manner that they are recycled and used repeatedly, they are often discharged from the process systems. It is desired that these compounds be removed from the waste water as completely as possible after the waste water is discharged from the process system. From the conventional general understanding of skilled workers, it is considered that substantially all surface active agents such as sodium alkylbenzene sulfonates (ABS), sodium alkyl sulfates and polyoxyethylene nonylphenyl ethers can be removed almost completely by subjecting waste waters containing these surface active agents to an activated carbon (activated charcoal) treatment, because they can be absorbed excellently by an activated carbon. For example, it has long been known that ABS can be effectively removed by the active carbon treatment. However, the above-mentioned sulfonated products, namely, condensates, with formaldehyde, of sulfonated aromatic compounds, fused benzene ring compounds and hetero compounds, can be removed only to a small extent by the active carbon treatment. In view of the fact that these compounds do not easily undergo biodegradation, the ineffectiveness of the active carbon treatment causes a serious problem of disposing of waste waters containing these compounds.